Echinacea for the Common Cold
February 1998; Volume 1: 16-20
By Jay K. Udani, MD, and Josh J. Ofman, MD, MSHS
The winter months, affectionately known as the "cold and flu season," are upon us. A hopeful flow of patients rolls in seeking the "cure for the common cold," or at least a prescription for antibiotics. Recent concerns about antibiotic resistance, as well as new evidence supporting the use of popular alternative remedies such as zinc supplements and vitamin C, have driven our patients to look outside the doctor’s office for help, and many have found the herb called echinacea.1Introduction/Tradition
Echinacea, also known as purple coneflower, is part of the daisy or aster plant family. It has been used for centuries by Native Americans for aches, colds, sores, and as an antiseptic and analgesic. The first reference to echinacea was in 1763 as "valuable in the treatment of saddle sores."
In 1887, echinacea was introduced into medical practice by a pharmacist, John Lloyd, and billed as a cure for a long list of medical conditions including syphilis, gangrene, diphtheria, hemorrhoids, and snake bites. It wasn’t until the development of sulfa drugs in the 1930s that echinacea began to fade into obscurity only to re-emerge in the early 1990s when two clinical trials in Germany found that the botanical decreased the length and severity of the common cold.2,3
Pharmacology
Echinacea can be divided into seven active constituents: polysaccharides, flavonoids, caffeic acid derivatives such as echinacoside, essential oils, polyacetylenes, alkylamides, and miscellaneous chemicals. The components that are most important for the immunomodulatory effects are probably the polysaccharides, including inulin. One study, however, contends that the alkylamides rather than the polysaccharides are most active in immunostimulation.4
Mechanism of Action
The hypothesis that echinacea "stimulates the immune system" is based on a series of basic research studies examining echinacea’s effect on complement, T-lymphocytes, macrophages, and its direct anti-bacterial and anti-viral properties.
The immunostimulatory properties can be divided into non-specific immunostimulation and specific anti-microbial activity. The non-specific immune effects occur via three routes. First, echinacea protects the integrity of the hyaluronic acid extracellular matrix by blocking the depolymerization of hyaluronidase. Second, echinacea activates the alternate complement pathway via increased properdin, which then increases leukocyte and phagocyte migration. And, finally, echinacea promotes non-specific T-cell activation by binding to T cells and increasing interferon production—which, in turn, increases T-cell replication, macrophage activity, and the number of circulating neutrophils.5
Echinacea has been shown to have only mild activity against specific bacteria;6 however, it does have antiviral activity against influenza, herpes, and vesicular stomatitis viruses.7 It is most likely that the immunostimulatory effects rather than the specific anti-bacterial or anti-viral properties account for the health effects of echinacea.
Clinical Studies
We searched MEDLINE, AIDSLINE, CINAHL, textbooks, and the Internet using keyword "echinacea." Currently, all clinical literature regarding echinacea is in German, and no English translations are yet available of these data. Summaries of these reports revealed one trial that randomized 108 people with a history of three or more colds per year to receive echinacea (4 mL bid) or placebo for eight weeks.3 Those who received echinacea decreased their chance of contracting a cold by 36%; of those who did become symptomatic, one-third noted fewer moderate to severe symptoms.
Another widely quoted study randomized 180 participants who presented with cold and flu symptoms to receive echinacea at 450 mg qd, 900 mg qd, or placebo.2 At high doses (900 mg qd), the signs and symptoms of colds decreased by 75% after three days as compared with only 37% in the placebo group. No difference was seen with the lower dose of echinacea.
Formulation/Dose
Echinacea is supplied as either a tincture (usually made with grain alcohol or myrrh), freeze-dried extract in tablet form, tea, or injection. These are all made from the above-ground portions or root of the flowering plant. A recent German study showed the same immunostimulatory effects in vivo with the injectable form, the tablets, and tinctures.
Most patients are more likely to use the tablets or capsules, which are readily available in most pharmacies and do not involve measurements and dilutions. We were unable to locate standardized dosages or concentrations of the teas or injections.
Advocates believe echinacea should be started at the first onset of cold symptoms and continued for 10-14 days at the dosage of 300 mg po tid. Others believe that the usual adult dose is a dropperful of tincture in water four times a day or two capsules of freeze dried extract four times a day. There has been speculation and concern that echinacea loses its effectiveness if taken continually for more than 2-3 weeks. We found no data, in vivo or in vitro, to support or refute this theory.
Adverse Effects
Echinacea is apparently a benign substance. Reported side effects include GI upset and diarrhea, as well as skin rash when used topically. There are no mutagenic properties, and the LD 50 is 50 mL/kg body weight in mice and rats. If given IV, echinacea has been found to produce a temperature elevation, presumably secondary to increased interferon and interleukin activity.8 The German government, however, advises people with impaired immune response to avoid immunostimulants, including echinacea. There are no known drug interactions and or other contraindications.
Conclusion
Echinacea is a popular therapeutic agent that has cycled in and out of favor over the centuries. The most popular usage is in the prevention and treatment of the common cold or flu, and there is substantial in vitro evidence to support a number of immunomodulatory effects. However, there are only scant data from two small human clinical trials to support its efficacy. The shortage of good clinical data raises concern about the validity of claims in books and articles that cite these studies as persuasive scientific evidence.
The most important clinical feature of echinacea is that there appear to be no significant adverse effects or mutagenic properties. Its usefulness in decreasing the incidence or severity and duration of symptoms of the common cold or flu warrants further investigation. Given the paucity of other options for cold and flu sufferers, and the absence of harmful effects, it may be worthwhile to recommend a trial of echinacea in addition to traditional supportive measures to those on the verge of cold or "flu."
References
1. Carper J. Miracle Cures. New York: Harper Collins; 1997:108-119.
2. Braunig B. Echinacea purpurea radix for strengthening the immune
response in flu-like infections. Zeitschrift Phytother 1992;13:7-13.
3. Schoneberger D. The influence of immune stimulating effects of pressed
juice from echinacea purpurea on the course and severity of colds. Forum
Immunologie 1992;8:2-12.
4. Bone K. Echinacea: What makes it work? Alternative Med Rev 1997;2:87-93.
5. Stimpel M. Macrophage activation and induction of macrophage cytotoxicity
by purified polysaccharide fractions from the plant echinacea purpurea.
Infect Immun 1984;46:845-849.
6. Wildfeuer A. The effects of plant preparations on cellular functions
in body defense. Arzneimittelforschung 1994;10:361-366.
7. Wacker A. Virus inhibition by echinacea purpurea. Planta Med.
1978;33:89-102.
8. Tragni E, et al. Evidence from two classic irritation tests for
an anti-inflammatory action of a natural extract, echinacea. Food Chem
Toxicol 1985;23: 317-319.
Dr. Ofman is Director of Pharmacoeconomics and Technology Assessment,
Zynx Health Inc. in Beverly Hills, CA, and a member of the faculty of Cedars-Sinai
Department of Medicine in Los Angeles. Dr. Udani is the Chief Resident,
Internal Medicine, at Cedars-Sinai in Los Angeles.
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